Method of preparing 2-mercapto-4-secondary amino pyrimidines



Patented Mar. 2, 1954 METHOD OF PREPAR ING 2-MERCAPTO-4- SECONDARY AMINO PYRIMIDIN ES George H. Hitchings,

roughs Wellcome & o.

hoe, N. Y., a 'corporatio Tuckahoe, and Peter Byrom Russell, Crestwood, N. Y

assignors to Bur- (U. S. A.) Inc., Tuckan of New York No Drawing. Application December 12, 1951, Serial No. 261,394

4 Claims. (Cl. 260-2565) This invention relates to novel 4-aminopyrimidine derivatives and a new and improved method of preparing them. It is particularly concerned with the discovery of novel products formed by the reaction of dimercaptopyrimidines with the primary amines which are found to have valuable pharmacological properties and are useful intermediates in synthesizing other 4-amino pyrimidine derivatives. This is a continuationin-part of our copending applications Serial No. 33,677 and Serial No. 33,678, now abandoned.

The present method is based upon the recognition that primary amines react readily with 2,4- dimercaptopyrimidines to form the corresponding z-mercapto-4-aminopyrimidine directly and without the difiiculties of previous methods which form inseparable mixtures due to the nearly equivalent reactiveness of halogen substituents in the 2-4 positions of the pyrimidine ring.

In accordance with the present invention it is found that primary amines react with 2,4-dimercaptopyrimidines to produce the corresponding 2-mercapto-4-aminopyrimidine to the exclusion of 2-amino substituted components. This reaction may be represented by the equation:

wherein R is a radical selected from the class consisting of alkyl, and monocyclic aryl and aralkyl radicals, R is a radical selected from the class consisting of alkyl groups and hydrogen, and R is a radical selected from the class consisting of alkyl, monocyclic aryl and aralkyl radicals and hydrogen.

When the 2,4-dimercaptopyrimidine compounds contain bulky substituentsat the 5 position the reaction does not always follow the same course and in some cases may be inhibited. Reactions of ZA-dimercaptopyrimidines with ammonia and secondary amines follow a somewhat different course and such reactions are the subject of other applications.

A considerable number of dimercaptopy-rimidine derivatives are amenable to this reaction having, for example, the general tautomeric formulae SIH St R' N both of which undergo the same reaction with the primary amine and wherein R and R. have the same values as previously indicated. Accordingly, the desired 2-mercapto-4-primary amino substituted pyrimidine may be prepared by the selective action of a primary aliphatic or aromatic amine with a 2,4-dimercaptopyrimidine either unsubstituted or containing a substituent at the 5 position of the pyrimidine ring, whereby the 4-mercapto group is smoothly replaced by the amine to give the corresponding 2-mercapto-4- amino derivative. In these reactions, the 2-mercapto group is not easily replaced by the amino group, thereby avoiding undesirable mixtures in the reaction product. The 2-mercapto group is amenable to replacement by hydrogen, hydroxyl, alkyl-mercapto and other groupings to form other compounds of pharmacological importance.

A particular advantage of the invention resides in the fact that it is possible to obtain a new group of 4-aminopyrimidine compounds having valuable pharmacological properties. These compounds, in accordance with the invention, may be formed by reacting a 2,4-dimercaptopyrimidine compound with a primary amine of the above formula. The new 2-mercapto-4- primary aminopyrimidines formed in accordance with the teachings of the present invention may be converted without difiiculty into many useful products of pharmaceutical interest.

The desired 2-mercapto-4-primary aminopyrimidine compound may be readily formed by merely heating the selected reactants under suitable conditions of temperature and pressure depending on the nature of the amine until the reaction is complete. The 2,4-dimercaptopyrimidine derivatives in many cases react readily at a temperature of about 100 to give yields of percent to percent of the corresponding it-amino derivatives. In most cases the reaction mixture may be heated or refluxed in an open system depending on the boiling point of the amine until the reaction is complete.

A considerable excess of amine is added to the reaction mixture. Suitable proportions for carrying out the reaction may be in general about three mols of the base to about one mol of the ZA-dimercaptopyrimidine derivative. The mixture becomes homogenous at once with the evolution of heat due to initial salt formation. Application of heat is usually continued for a period of about three hoursto complete the reaction.

The desired 2-mercapto-4-primary aminopyrimidine compound may be isolated from the reaction mixture by a number of methods including simple filtration from solution, evaporation of the solution to dryness, followed by crystallization from water or alcohol and simple precipitation of the material from solution with water or in some casesby removal of the excess base from the reaction mixture with ether. The preferred method of isolating the product will depend largely on the physical properties of the particular base used in the reaction.

The nature of the group R of the amine/does not appear to materially affect the course of reaction. For example, tetradecylamine reacted readily with the 2,4-dimercaptopypyrimidine. The reaction also proceeded smoothly to completion in the case of hydroxyamines such as ethanolamine. Moreover, the presence of a tertiary amino group as in beta-diethylaminoethylamine did not preclude the reaction although the yield of the final product was somewhat lower.

The presence or absence of a substituent other than hydrogen at the 6 positionof the pyrimidine ring also did not seem to materially aflfect the course of reaction as will be apparent from the specific examples'to follow;

The aromatic primary amines react readily with 2,4'-dimercaptopyrimidine derivatives with the evolution of hydrogen sulphide when combined at reflux temperature. For example, in the case of aniline and its derivatives, there was no indication of reaction at lbut when one mol of S-methyldithiouracil was heated with three mole of aniline at the refiux'temperature, the reacticnproceeded smoothly'to give a 90 percent yield of pure 2-mercapto methyl=4=anilinopyrimidinewhile other anilines reacted with equal facility.

The following examples illustrate specific in:- stances of the various applications in accordance with the present invention.

Example 1 1.3 g. of 5*methyldithiouracil was heated'with cos. of a 33 percent aqueous methylamine solution in abombat 100 for three and one halfhours. The-contents oi the tube was evaporated to-dryness. dissolved and-crystallized a number oftimes from hot aqueous solution to recover'a 60 percent yield of 2-mercapto-5-methyl-4= methylaminopyrimidine.

Example 2.

The procedure of Example 1 was repeated-with 5-n-amyldithiouracil to form 2'-mercapto-5-namyli-methylaminopyrimidine in 75 percentyield, M. P. 198.

Example 3 Em'ampl'e 5 The procedure of Example. 1 was again re peated using S-ethyl-fi-nepropyldithiouracil to form a5 0 percent yield, of 2emercapto+5i-ethyl '-6-'- n-propyl-4-methylaminopyrimidine..

'through with 5-ethyl-G-phenyldithiouracil to Example 6 The procedure of Example 1 was repeated using 5-ethyl-6-phenyldithiouracil to form a percent yield or: 2-mercapto-5-ethyl-6-phenyl-4- methylaminopyrimidine.

Example 7 0.75 g. of 5'methyldithiouracil and 3.5 g. of tetradecylamine were combined and heated at about 100 over a water bath with the evolution of hydrogen sulphide for a period of about three hours; The excess base was dissolved and extracted with ether and the residue recrystallized several times from ethanol to form needles of 2 mercapto 5 methyl 47- tetradecylaminopyrimidine. I

Example 8,

The procedure of Example 7 was repeatedzusing: S-hexyldithiouracilto. produce anpercentyield of 2 mercapto fi-hexyl i tetradecylamirioe pyrimidine.

Example 9 The procedure of Example 7 was repeated using 5,6-dimethyldithiouracil to producea 50.-per.cent; yield of 2-mercapto-5-tetradecyl-6-methyl=- tetradecylaminopyrimidine.

Example 10 0.75 g. of 5-methyldithiouracili and. 331g. of. benzylamine were mixed together and heatedat over a water bath for a periodofjaboiit three.- hours. A yield of 60 percent Z-mercaptO-5- methyl-e-benzylaminopyrimidine was recovered by extraction and crystallization.

Example 12 The procedure of Example 11 was carried form a 60 percent yield of 2-mercapto 5-ethyl-6- phenyl-4-benzylaminopyrimidine.

Example, 13

0.95 g. of 5-propyldithiouracil washeated with- 4.5 g. of beta-hydroxyethylamine. over a water bath with the evolution of hydrogen sulphide fora period of three hours. Theexcessbase was extracted as before and the 2 mercapto 5 propyl--beta-hydroxyethylaminopyrimidine fe covered in about 80 percent yield.

Example 14 The process of the precedingexample. was fe=- peated with 5-inethyl 6 phenyldithimiraci1 re form an 85 percent yield of 2'-mercapto:-5=methyl= -6-phenyl-4-beta-hydroxyethylaminopyrimidine.

Example 15 Example. 16 The procedure of Example 15 was repeated 7 using 5-methyl-fi-phenyldithiouracil to give a 75 percent yield of Z-mercapto--methyl-6ephenyl- Example 18 0.65 g. of dithiouracil and 3.3 g. of tetradecylamine were mixed together and heated at 100 in a water bath with the evolution of hydrogen sulphide. The reaction was allowed to continue at this temperature for a period of three hours for completion of the reaction. The excess base in the reaction mixture was extracted with ether and the residue dissolved and recrystallized several times from ethyl alcohol to give a yield of about 80 percent. The 2-mercapto-4-tetradecylaminopyrimidine appeared as colorless needles having a melting point of 148l49.

Example 19 The process according to Example 18 was repeated using n-amylamine as a reagent. The product obtained on crystallization was 2-mercapto-4-n-amylaminopyrimidine, melting point of 218.

Example 20 The process according to Example 18 was repeated using benzylamine as the base. The product obtained on crystallization was 2-mercapto- 4-benzylaminopyrimidine, melting point of 248- 249.

Example 21 The process according to Example 18 was repeated using beta-methylhexylamine to produce 2 mercapto 4 beta methylhexylaminopyrimidine.

Example 22 The process of Example 17 was repeated using n-propylamine with 2,4 dimercapto 6 ethylpyrimidine to give 2-mercapto-6-ethyl-4-propylaminopyrimidine.

- Example 23 The procedure set forth in Example 17 was repeated using n-hexylamine and 2,4-dimercapto- G-phenylpyrimidine to give 2-mercapto6-phenyl- 4-n-hexylaminopyrimidine.

Example 24 0.65 g. of dithiouracil and 1.76 g. of beta-diethylaminoethylamine were brought together and heated at a temperature of about 100 until the reaction was complete. The excess base was washed away with ether, the residue treated with water and the product crystallized from solution. On recrystallization from ethyl alcohol, a 50 percent yield of 2-,mercapto-4-beta-diethylaminoethylaminopyrimidine was obtained in the form of plates having a melting point of 114-115.

Example 25 The process of Example 18 was again repeated using beta-hydroxyethylan-line as the base to form 2 mercapto 4-beta-hydroxyethylaminopyrimidine, melting-mint of 2269-2289.

Example 26 0.65 g. of G-methyldithiouracil and 2 cos. of aniline were refluxed for three hours. The excess aniline was removed with ether and the product washed with ammonia to dissolve any unchanged dithio compound. The product recrystallized from water was Z-mercapto-fi-methyl-4- anilino- 230 0.; the yield was Example 27 The process of Example 26 was followed using 'fi-n-amyldithiouracil and aniline as reagents to give 2-mercapto-6-n-amyl- 4 -anilinopyrimidine, M. P., 227-228.

pyrimidine, M. P.

Example 28 ,The process of Example 26 was followedwith 6-phenyldithiouracil to give 2-mercapto-6-phenyl-4-anilinopyrimidine.

Example 29 The process of Example 26 was followed using G-phenyldithiouracil and tetradecylamine to give 2 mercapto 6 phenyl 4 tetradeoylaminopyrimidine.

Example 30 Dithiouracil was refluxed with a molar excess of aniline to form 2-mercapto-4-anilinopyrimidine. The yield was approximately percent and melting point 285".

Example 31 Dithiouracil was combined with an excess of p-Cl-aniline in an open system at a temperature of 180. The yield was about 90 percent of 2- mercapto-4-p-chloroanilinopyrimidine having a melting point of 299.

. Example 32 G-methyldithiouracil amylamine vat mercapto 6 methyl 4 n amylaminopyrimidine havinga melting point of 221. I

r I Example 33 6-phenyldithiouracil was combined with namylamine at a temperature of 100 in an open system to give a '70 percent yield of 2-mercapto-6- phenyl-4-n-amylaminopyrimidine having a melting point of 227228.

Example 34 G-phenyldithiouracil was reacted with p-meth oxyaniline-at a temperature of to give an 82 percent yield of 2-mercapto-6-phenyl-4p-meth- 'oxyanilinopyrimidine of melting point 264-265 The examples outlined above are merely illustrative of methods conveniently employed in preparing the compounds of the present invention and it will be appreciated-that other equally feasible methods maybe utilized.

Other examples of compounds falling within the scope of the present invention which may be pre-v pared by similar procedures are the following: (35) 2 mercapto 5 methyl 4 n amylaminopyrimidine (36) 2 mercapto 5 methyl 4 anilinopyrimidine (37) '2 mercapto 5 methyl 4 methyla-minopyrimidine (38) 2 mercapto 5 methyl 4 ethylaminopyrimidine 2 4 mercapto 5 methyl 4- beta hydroxyethylaminopyrimidine (40):-2 mercapto 5 methyl 4 beta methylaminoethylaminopyrimidine' was combined with ntogive a 75 percentyield of' 2- (41) 2 mercapto 4 5 methyl 4 beta diethyle-minoethylaminopyrimidine (42) 2 mercapto 5 -,methyl 4 1 beta (.4?

morpholino) ethylaminopyrimidine (43) 2 mercapto 5 methyl 4 p chlaro- 5'.

anilinopyrimidine 4) 2-mercapto 5 methyl 4 11- methoxyr anilinopyrimidine (45) 2 mercapto 5 methyl 4 p methylanilinopyrimidine 10,

(46) 2 mercapto 5,6 dimethyl 4 methylaminopyrimidine- (47) 2- mercapto 5 6- dimethyl 4-inaminopyrimidine (48) 2 mercapto pyrimidine (49) 2- mereapto 5,6 dimethyl 4 beta diethylaminoethylaminopyrimidine (50) 2 mercapto 5,6

butyle 5,6 dimethyl 4 anilineoxyanilinopyrimidine (51) 2 mercapto 5,6 dimethyl 4 benzylaminopyrimidine (52) 2 mercapto 5,6 dimethyl 4 anisylaminopyrimidine (53) 2 mercapto 5,6 dimethyl 4 p chloroanilinopyrimidine (54) 2 mercapto 5 ethyl 6 methyl 4 4- ethylaminopyrimidine (55) 2 mereapto 5 ethyl 6 methyl 4- benzylaminopyrimidine (56) 2 mercapto 5 ethyl 6 methyl 4 n octadecylaminopyrimidine (5T?) 2 mercapto- 5 n butyl 4 n; eicosylaminopyrimidine.

(58) 2 mereapto 5 ethyl 6- phenyl 4- n octadecylaminopyrimidine (59) 2 mercapto 5 methyl 6 beta dimethylaminopyrimidine (60) 2 mercapto 5 n butyl 6 phenyl 4 isopropylaminopyrimidine.

(61) 2 mercapto 5 methyl 4 homovera- 6 thyl phen 4 (68) 2 mercepto 5 methyl 4 (2,5 dimethoxyphenethylamino) pyrimidine (69) 2 mercapto 5 methyl 4 (2,3 dimethoxyphenethylamino) pyrimidine dimet-hyl 4 pmeth-.

wherein R is a radical selected from the,;ela,ss

(70)-2- merca-pto 5 methyl 4 (2,4 di= methoxyphenethylamino) pyrimidine (71) 2 mercapto- 5,6 dimethyl- 4 homoanisylaminepyrimidine (72) 2- mercapto 5 n butyl 6 methyl 4 anisylaminopyrimidine (73) 2 mercapto 5 ethyl 6, p chlorophenyl 4 n hexadecylaminopyrimidine;

('14) 2 mercapto 6 ethyl 4 beta hydroxyethylaminopyrimidine (75) 2 mercapto 6 p methoxy-phenylx- 4- ethylaminopyrimidine ('16) 2 mer p w 6 p 0 y prowl-.-

aminopyrimidine ('17) 2 mercapto 6. methyl droxyethylaminopyrimidine ('18), 2 mercanto 6 phenyls 4 n eiQosy-b a i opy imidine (79): 2 mercaptd 61'! to .-t methoxyphenyl s 4- n hexadecylaminopyrimidine (80) 2 mercapto 6 4 o bromophenyl 4 beta hydroxyethylaminopyrimidine 81) 21- memento. 6. n propyl n, hutylaminoe hyleminopyrimidine (82') 2. mercapto. 6 m bromophenyl 4 (2,4. dimethqxyphenethyl) aminopyrimidine 3 2- mexcapto. (i n p opyl 4 enzylaminopyrimidine. (84) 2 mercapto 4 n octadecylaminopyimidiner (85) 2- mercapto P 4 ethylaminopyrimidine (86) 2 mercapto 4 n eicosylaminopyrimidine (83x)i 2V vmemento 4 -viso amylaminopyriminet (8%) 2' mercaptoh- 4 tart. hutylaminopyrimi- .(89) 2 mercepto 4 sec. butylaminopyrimidine.

(90), 2- memento 4- (beta hydroxy iso. pro:

pyleminq) pyrimidine (91) 2, memento- 4 gamma hydroxypropyle aminopytin i lme (92) 2V me capto- 4 -r beta 1 dimethylaminothylemin py idm (93-) 2 mercapto 6 n propyl 4 homoyeratrylamino pyrimidine (94) 2 mercapto 6 methyl 4 octadecylamine py i n We claim:

v 1. The method of preparing 2-mercapto-4-secondary aminopyrimidines which consist in reacting a 2,4-dimercaptopyrimidine with a primary amine.

2. The method of preparing compounds of the formula- NHR consisting of alkyl and monocyclic aryl and aralkyl radicals, R is a radical selected from the less; ement ng f lkyl emuns .andhydrogen. aneflti isa radi elselected from the class oom s ne .e kyh monecyelie aryl and arallryi radi-i cals and hydrogen, which comprises react nga primary amine of the formula, NI-leR. with a dithiopyrimidine of the formula wherein R R31 and R have the above mentioned values.

3; Themethod settforth in claim-1 wherein anexcessof the-amine is employed.

4. The method set forth-in claim 1 wherein the reaction takes place at about GEORGE H. HITCHINGS. PETER BYROM RUSSELL.

Reierenees Cited in the file of' this patent- Seh1enker,-Ber. Dent. Chem., 34-, 2821' (1901).

"* Gabriel et aL, Ber-t Dent. Chem., 32,.2930'fl899),

-4t-betal-di-r 

2. THE METHOD OF PREPARING COMPOUNDS OF THE FORMULA 